DESCRIPTION: Members of the bacterial genus Bdellovibrio are obligate predators of other Gram negative bacteria. They follow a biphasic life cycle with a free swimming attack phase and an intracellular growth phase. Nothing is currently known regarding gene regulation in bdellovibrios, indeed little is known about their genetics in general. However, a system for introducing DNA into bdellovibrios has recently been reported, making some genetic approaches possible in this organism. The investigator proposes to isolate and characterize conditional mutants that have lost the ability to produce plaques on lawns of susceptible prey cells. The overall objectives are to isolate temperature-sensitive (ts) mutants of the developmental cycle of the bdellovibrios, to characterize those mutants, and to isolate and characterize mutant DNA sequences. Bdellovibrios will be chemically mutagenized, and mutants unable to produce plaques at 34 degrees C but able to plaque at 20 degrees C will be isolated. Each mutant isolated will be characterized according to which phase in the developmental cycle is blocked. Mutants unable to penetrate into the prey's periplasmic space will be further examined for altered enzymatic activity of penetration-specific enzymes. Mutants from each category will be mated with E. coli carrying wild-type Bdellovibrio genomic libraries in transmissible vectors. Conjugants that have regained the ability to produce plaques at 34 degrees C will be isolated, plasmid DNA extracted and mutant sequences characterized by restriction analysis and DNA sequencing analysis in comparison to wild-type sequences. Sequences obtained will be screened against known sequences in Genbank for homology. Identification with homologous sequences may suggest possible functions of the gene products involved. This work provides an initial step towards understanding the nature of the Bdellovibrio-prey cell interaction.